1. Field of the Invention
The present invention relates to a semiconductor device and manufacturing method therefor, and more specifically to a semiconductor device that is mounted to a board by means of a TAB tape with bump and a manufacturing method therefor.
2. Description of Related Art
In the past, such a semiconductor device was disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 8-30869 as proposed by the inventor of the present invention. This semiconductor device, as shown in FIG. 3, is manufactured by mounting a semiconductor chip 2 onto an insulating base film 4 made of polyimide or the like.
More specifically, on both sides of the base film 4 in the latitudinal direction sprocket holes 15 are provided for the purpose of transporting and positioning the base film 4, these sprocket holes 15 being usable to move the base film 4 in its longitudinal direction.
The base film 4 has an aperture for the positioning the semiconductor chip 2, this being a device hole 1 which is provided in the inside thereof, and cut holes 16 being formed around the outside of this device hole 1.
On the base film 4 between the device hole 1 and the cut holes 16, are formed lands 17, which are electrically connected to the semiconductor chip 2 by inner leads 18. On the lands 17 ball-shaped bumps 10 are formed of solder or the like, to form material for forming external connection electrodes.
As shown by the broken line in FIG. 3, the partitioned area other than at the bumps 10 is covered by a cover resist 9, this cover resist 9 preventing the contamination of the inner leads 18, for example.
The semiconductor chip 2 and the inner leads 18 around the periphery thereof are sealed with a resin.
Finally, by cutting the base film 4 away from the cut holes 16, a semiconductor device formed by the semiconductor chip 2 and the base film 4 is obtained.
In a semiconductor device having the above-noted configuration, because it is possible to mount the bumps 10 on top of the lands 17 directly to a printed circuit board 20, the base film material can be substantially used as a package material.
Therefore, compared to a semiconductor device having a package of ceramic or the like, this device offers the advantage of low cost. Also, because the wiring region of the inner leads 18 is limited to an area formed inside of the cut holes 16, it offers an advantage in compactness as well.
Another example from the past is shown in FIG. 4, in which there is an improvement in heat dissipation. In this device, a wire which is flush with the same plane as the inner leads 18 within the device hole 1 suspends a suspended lead 22, onto which is formed a heat-radiating bump 25, which radiates heat to the printed circuit board 20, a heat-radiating plate 24 and heat sink 21 being mounted to improve the heat dissipation.
In a semiconductor device as described above, because the inner leads 18 and the solder bumps 10 are disposed on one and the same plane, a terminal disposed outside of the package, for example, would have a long wiring length, resulting in a deterioration of electrical characteristics with regard to inductance (L) and the like.
With increases in speed, there are particular problems with faulty operation if ground leads are not made short to reduce the influence of noise. Thus, it is necessary to make the wiring length as short as possible, to improve its electrical characteristics.
To achieve this, a two-metal TAB tape, having metal layer on the reverse side of the base film is used, ground wires being connected by means of a through hole, thereby improving the quality of grounding to improve the electrical characteristics.
However, when this two-metal tape is used, the TAB tape cost rises, making practical use of this method difficult.
On the other hand, in the Japanese Unexamined Patent Publication (KOKAI) No. 8-51128, although a bumped array TAB package is disclosed, it simply shows a TAB tape comprising one conductive layer which is patterned so as to form wiring connected with each one of the pads arranged on the tape in an array configuration.
However, it fails to show or suggest a technical feature of making use of a conductive metal layer formed just below a semiconductor chip.
The Japanese Unexamined Patent Publication (KOKAI) No. 8-97254 shows a method for mounting a semiconductor on a printed board in that on a surface of an insulating resin film formed in an area surrounded by a plurality of device holes in the TAB tape, lead wires are formed.
However, it fails to show or suggest forming a metal film over all of the surface of the area to be used for a grounding wire.
As mentioned above, in accordance with these prior arts, signal wires and grounding wires should be formed on one surface of the TAB tape with relatively long lengths thereof and thus preventing minimizing the semiconductor device.
In view of the above-described drawbacks in the prior art, an object of the present invention is to provide a semiconductor device having an economic configuration, with a minimal wiring length to improve the electrical characteristics thereof, and a method of manufacturing this semiconductor device.